Why your phone shouldn't go swimming

On a lake trip over July 4th weekend, my daughter's iPhone 7 Plus ended up taking a dive. It was found in about 3 feet of water 24 hours later, still working but with some permanent damage. The experience provided a few lessons.

Immersion in water used to ruin a cellphone. That's less true today because many newer phones are "water-resistant" (see tinyurl.com/y4gyjmxr) — but they are still not "waterproof." Water-resistant phones are only designed to survive underwater for a while, under certain conditions. And most cellphone warranties still don't cover water damage.

Be a little skeptical about water-resistant phones. Samsung was criticized for allegedly exaggerating the after-immersion performance of its water-resistant phones (see tinyurl.com/y2n3g2qh). Those phones were rated IP68, meaning they should survive 30 minutes underwater at a depth of 4.9 feet, or 1.5 meters. (See ratings at tinyurl.com/yyew9fc6).

That raises an interesting question: What can you expect from a phone that has spent some time underwater? I was surprised when my daughter's phone emerged from the lake with its screen glowing and still worked — mostly. To appreciate my surprise, consider that the iPhone 7 Plus is an "older" device whose water-resistant qualities are less robust than today's phones. Apple said the phone can withstand 30 minutes in 3 feet of water (its rating is IP67). But it actually survived 48 times that long.

While that was impressive, the iPhone still had problems:

• The phone's camera suffered the most. Some moisture had gotten inside, which meant the camera took hazy photos. This seemed to improve when the iPhone had been dry a while, but then the haziness returned.

This underscored something I had learned years ago, when moisture seeped into the camera on my iPhone 5 during normal operating conditions: The camera is the most vulnerable part of a phone, and even a tiny bit of water will ruin it. (In that case, Apple replaced the phone because it was judged to have a manufacturing flaw rather than water damage.) The damage to my daughter's iPhone suggests that the camera remains its most vulnerable part, even in the age of water-resistant phones.

• At first, the phone's screen was "jumpy" and the phone would shut down unexpectedly. This was probably because moisture had affected the battery (I could easily restart the phone by plugging it in). But those problems also disappeared in a few days.

• The phone's cellular and Wi-Fi connections worked perfectly.

• My daughter's chief concern was whether she could retrieve the thousands of photos stored on the phone. Fortunately, the phone's flash memory was unaffected, and all the photos were still there.

As it turned out, my daughter's photos had been backed up earlier to iCloud, Apple's online service — but only because she had paid extra for enough online storage to hold thousands of photos. If your phone has a lot of photos, think about whether you have backed them up — before your phone goes swimming.